ATR and hepatocellular carcinoma: The abscopal effect remains a topic to debate in immunotherapy combined with RT for HCC therapies because certain mechanisms, such as ATR-mediated CD47 and PD-L1 upregulation, have been proposed as potential constraints on radiation-induced immune activation.22 The absence of a clear abscopal effect resulted in not significantly improved tumor control in the outfield of SBRT/PBT.